Control system and unloading method

ABSTRACT

A control and method of use implemented by an unloading mechanism for unloading products from an intermediate container onto a conveyor for downstream processing. The controls tilt the mechanism, in embodiments, to a relative angle from a horizontal or supporting surface and proximate the conveyor. A gate is controlled to slidably mount between an open position and a closed position in order to allow product slide from the structure.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional ApplicationSerial No. 60/372,787, filed on Apr. 17, 2002, the entire contents ofwhich are herein incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to a control system andmethod of unloading containerized cartons and mail trays and the likeusing an unloading mechanism and, more particularly, to a control systemand method of use for automatically unloading mail trays, packages andthe like from an intermediate container onto a conveyor for downstreamprocessing.

[0004] 2. Background Description

[0005] The sorting of mail is a very complex, time consuming task. Ingeneral, the sorting of mail is processed through many stages, includingfront, middle and back end processes. The front end process, forexample, is used to orient and align mail trays; whereas, the middle andback end processes are used for the sorting and processing of the mailfor future delivery. These processes can either be manual or automated,depending on the mail sorting facility, whether it is a postal facilityor other delivery or transportation facility. A host of factors may alsocontribute to the automation of the mail sorting facility, frombudgetary concerns to modernization initiatives to access to appropriatetechnologies to a host of other factors.

[0006] In general, however, most modern postal facilities have takenmajor steps toward mechanization (e.g., automation) by theimplementation of a number of technologies. These technologies include,amongst others, singulators, letter sorters, facer-cancelers, automaticaddress readers, parcel sorters, advanced tray conveyors and flatsorters. As a result of these developments, postal facilities havebecome quite automated over the years I an effort to reduce costs.

[0007] In implementation, prior to the front end process, an operatormust first remove containers, mail trays, packages and the like(referred to generally as mail trays) from intermediate containers ormail carts. Once removed from the intermediate containers, the mailtrays are placed on a conveyor, at which time they are oriented andaligned into a single file for downstream processing. This orienting andaligning step is typically referred to as the front end process.However, this manual step of placing the mail trays onto the conveyor istime consuming, labor intensive and hence adds further expense to thesorting and delivery processes.

[0008] In order to provide automation for this stage of processing, somefacilities have implemented a robotic arm and end effector used toremove the mail trays from the intermediate containers. The robotic armand end effector mechanism typically removes one mail tray at a time or,alternatively, a single layer of mail trays at a time. The robotic armand end effector is very expensive to manufacture, including the controlsystems and the mechanical features. It is also known that these roboticarm mechanisms are constrained by its gears and other mechanicalfeatures, making the robotic arm slow, cumbersome and costly frommaintenance stand point. It has also been found that a robotic armcannot effectively and efficiently unload mail trays which areirregularly stacked in the mail cart.

[0009] In another known removal system, a lifting mechanismhydraulically lifts the intermediate container and then dumps out of thetop of the container, at one time, all of the mail trays onto theconveyor. This process, though, results in damage to the mail trays,mail trays falling off the conveyor, itself, as well as bar codesfalling off the mail trays. This process is also susceptible tointerference from shelves associated with the intermediate container.

[0010] As an alternative, a system can be employed which empties traysout of the front of the container instead. One such system is disclosedin U.S. patent application Publication US 2002/0150452A1. In thissystem, a cage of holding device is provided for holding containers.This holding device includes an open side which has a sliding wall orgate that is disposed over the open side. The holding device along withthe container is tilted such that the open side of the container isgenerally directed downward. From this tilted orientation, the slidingwall or gate is withdrawn, exposing the open side of the container. Thispermits the egress of the packages, etc., from the container. However,while this system has utility on its own, the functionality of thesystem can be enhanced. First, when the holding device is tilted, thegate has a tendency to drive against the floor at certain angles, thuspreventing the holding device from further tilting, jamming the gate orotherwise disrupting the operations of the apparatus. Second, during thetitling mode the packages are typically thrown or tossed from thecontainer in a disjointed manner thus making it difficult to provide aproper ordering of the packages for future bar code reading.

[0011] Once the mail trays are placed on the conveyor, the front endprocess then orients and aligns the mail trays so as to allow the mailtrays to be conveyed to other stations for scanning, preparation formail processing and future delivery. To accomplish this, a “singulator”is employed which is capable of manipulating the mail trays into asingle file. Known singulators include, for example, cascading metalchutes incorporated at right angles, metering belts, skewed rollers andother mechanisms. However, in these systems, the footprint or layout isquite large (e.g., exceeding 100 sq./ft), and cannot easily be fittedwithin a confined floor space.

[0012] The present invention solves one or more of the above problems.

SUMMARY OF THE INVENTION

[0013] In a first aspect of the present invention, a method of unloadingproduct from an intermediate container onto a conveyor for downstreamprocessing/is provided. The method includes loading a mail cart havingthe product into the holding structure. The holding structure is thentilted at a relative angle, in embodiments to approximately 30° withrespect to a horizontal surface. The gate is incrementally opened toallow one layer at a time of product to slide from the mail cart andexit from the holding structure. A determination is made as to whetherthe one layer of product has exited from the holding structure and ontothe conveyor. If so, then the opening of the gate and the determinationstep are repeated until the gate has realized its full open position.

[0014] In another aspect of the present invention, a control system forcontrolling the unloading of product from an intermediate container ontoa conveyor for downstream processing is provided. The control systemcomprises:

[0015] (a) a module that controls tilting the unloading mechanism to arelative angle with respect to a supporting surface;

[0016] (b) a module that incrementally opens a gate of the unloadingmechanism to allow a single layer of product at a time to slide from amail cart within the unloading mechanism and exit therefrom onto theconveyor; and

[0017] (c) a module that controls determining whether the single layerof product has exited from the unloading mechanism and onto the conveyorand if the step (c) is affirmative, repeating the steps of (b) and (c)until all the gate has realized it full open position.

[0018] In embodiments, the module that controls tilting further controlsdetermining whether the relative angle of the unloading mechanism is atapproximately 30° with respect to the supporting surface. The controlthat controls incrementally opening of the gate further controls raisingthe gate to the closed position. In further embodiments, a module isprovided for controlling a relative angle of the unloading mechanism atapproximately 30° with respect to the supporting surface. A module isalso provided that controls raising the gate to the closed position,raising the unloading mechanism to an original position after the gatehas been fully opened as determined by a sensor, and returning theunloading mechanism to an original position after the gate has beenfully opened. A machine readable medium containing code is also providedfor performing unloading of product.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The foregoing and other objects, aspects and advantages will bebetter understood from the following detailed description of a preferredembodiment of the invention with reference to the drawings, in which:

[0020]FIG. 1 shows a general schematic diagram of the unloading systemimplementing the control and method of the present invention;

[0021]FIG. 2 shows a top view of the unloading system implementing thecontrol and method of the present invention;

[0022]FIG. 3 shows a side view of the unloading system implementing thecontrol and method of the present invention;

[0023] FIGS. 4 though 7 show the various stages of operation of theunloading system under the control of the control and method of thepresent invention; and

[0024]FIG. 8 is a flow diagram showing the steps of implementing themethod of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0025] The present invention is directed to a control system and methodof unloading containers. In general, the control system and method iscapable of unloading items such as cartons, packages and mail trays(referred to generally as mail trays) from intermediate transportcontainers or carts and onto the conveyor in a gentle, organized, smoothmanner. In one embodiment, the unloading system is used in conjunctionwith a take away conveyor which is inclined to (i) unstack mail trayswhich are “piggy-backed” (i.e., stacked on top of one another) after theunloading process and (ii) further enhance the “gentleness” of theunloading process.

[0026] Unloading System

[0027] Referring now to FIG. 1, a general schematic diagram of one typeof unloading system implementing the control and method of the presentinvention of the present invention is shown. It should be understoodthat the control and method of the present invention may be implementedwith other unloading mechanisms having a gate and tilting mechanism. Theunloading system is depicted generally as reference numeral 100 andincludes a frame 102 and a bottom supporting surface 104. Inembodiments, a closed top portion 105 is also provided in order toensure that mail trays and other types of packages will not be ejectedfrom the top thereof during the tilting operation. The frame 102 and thebottom supporting surface 104 (and, in embodiments, the closed topportion 105) form a general caged or holding structure which is capableof accommodating an intermediate transport container or cart 106.Although the cart 106 makes no part of the present invention, it isnoted that the cart accommodates items such as mail packages, mail traysand the like which need to be transferred to the conveyor for downstreamprocessing.

[0028] Still referring to FIG. 1, a gate 108 is slidably mounted to afront portion 109 of the holding structure, and more specifically to thefront portion of the frame 102. The gate 108 includes a ramp portion 110and a reverse hinge portion 112 at an opposing end. The reverse hingeportion 112 is adapted to move away from the bottom supporting surface104 as the gate 108, itself, is retracted or opened.. That is, thereverse hinge portion 112 will be capable of sliding along thehorizontal surface (e.g., a floor or other surface) upon contacting suchsurface. This ensures that the gate 108 will not be hindered, jammed orotherwise lock up during the unloading operation. At least one open side114 is provided on the holding structure in order to allow entry of thecart 106 into the unloading system 100 of the present invention. Inembodiments, a hinged ramp 116 may extend from the bottom supportingsurface 104, at the open side 114, so that a fully loaded cart 106 canbe easily rolled into unloading system 100 (i.e., into the holdingstructure).

[0029]FIG. 1 further shows a door 118 hingedly mounted to the frame 102via a hinge mechanism 120. In more specific embodiments, the door 102 ishingedly mounted to the frame 102 on the open side 114, and is designedto move back and forth between an open position (FIG. 1) and a closedposition (FIG. 3). In the closed position, a locking mechanism 122 suchas, for example, a latch mechanism, may be used for locking the door 118to the frame 102. This ensures that the cart 106 (and mail trays)remains within the holding structure of the present invention during thelifting and tilting operations.

[0030] In further embodiments, the frame 102 may be hinge mounted to asupporting structure (FIG. 4). This configuration allows the framestructure 102 to be moved into an open position so that the cart 106 canbe rolled onto the bottom supporting surface 104 allowing access to thefront of the cart. In this configuration, the holding structure may beslightly lifted from the floor in order to allow the operator to easilyopen and close the holding structure of the present invention. The ramp116 is still used to assist the user in carting the cart 106 onto thebottom supporting surface 104.

[0031]FIG. 2 shows a top view of the unloading system 100 of the presentinvention. In this view, a tilting mechanism 124 and a lifting mechanism126 are shown mounted between the frame 102 and a supporting structure128. Both the tilting mechanism 124 and the lifting mechanism 126 arepreferably hydraulically powered mechanisms; however, it should beunderstood by those of ordinary skill in the art that other mechanismssuch as stepper motors, screw drives and the like may also be used asthe tilting mechanism 124 and the lifting mechanism 126. The tiltingmechanism 124 is adapted to tilt the holding structure in the directionof the gate 108 to approximately 30° from a horizontal surface (i.e., asupporting surface of the holding structure). This tilt angle ensuresthat the mail trays will gently slide, not drop or tumble, in acontrolled manner from the cart 106 onto the conveyor. This tilt angle,in conjunction with the inclined take away conveyor, will also ensurethat the majority, if not all, of the mail trays will be oriented rightside up when unloaded onto the conveyor. It should be understood thatother tilt angles such as, for example, a tilt angle of approximately100 or otherwise may also be contemplated by the present invention. Inthese other tilt angles, there may be no need then to incline the takeaway conveyor, itself. In embodiment, it is thus accordingly understoodthat many different combinations of tilt angles and inclines of theconveyor are possible to ensure that the container contents gentlyslide, not drop or tumble, from the unloading system of the presentinvention. In embodiments, the supporting structure 128 providesstability to the holding structure 100 during the lifting and tiltingoperations.

[0032] A motor and drive system 130 may also be mounted to the frame 102in order to drive the gate 108 between an open position and a closedposition. The drive system 130 may be a screw type system, a rack andpinion type system or other drive mechanism. In the open position, achute or opening 129 is formed between the ramp 110 and an upper,horizontal bar 102 a of the frame 102. The chute 129, in embodiments, isapproximately 20 inches in length, but may equally be other lengths toaccommodate different sized mail trays, packages and the like. In anembodiment, the chute 129 is formed only after the holding structure istilted to 30° from the horizontal surface. The tilt angle in combinationwith the ramp 110 and the opening of the chute 129 is designed to allowa single layer of mail trays, at a time, to gently slide from the cart106 onto the conveyor in a controlled manner.

[0033]FIG. 3 shows a side view of the unloading system 100 of thepresent invention. As seen in this view, at least one or more photoeyeor other sensor 131 may be mounted to the frame 102 or other placementsuch as a conveyor rail to monitor the movement of the sliding gate andhence the removal of the mail trays from the unloading system 100 of thepresent invention. Additionally, the tilt angle may be governed by oneor more limit switches 138 mounted to the supporting structure 128 orthe frame 102. This ensures that the unloading system 100 of the presentinvention will tilt to a predetermined angle.

[0034] A hinged pivot 132 is provided between the frame 102 and thesupporting structure 128. By use of the combination of the tiltingmechanism 124 and the hinged pivot 132, it is possible to tilt theunloading system 100 of the present invention between various angles.Upright walls 134 may also be mounted to the frame 102, which furtherencloses the holding structure of the present invention.

[0035] A controller 136 is also shown in FIG. 3. The controller 136 maybe mounted remote from the frame or other placement, depending on thespecific applications. The controller 136 is designed to control thetilting mechanism 124, lifting mechanism 126 and the gate 108 inconjunction with the limit switches 138, proximity switches 140 (placed,for example, on the on the supporting structure 128) and photoeyes forthe conveyor. In embodiments, the controller 136 controls theincremental movement of the gate 108 through a predetermined distanceand at a predetermined velocity. For example, the controller 136 mayincrementally control the movement of the gate 108 between a closedposition and a completely retracted, open position. The gate 108retracts in predetermined increments to allow only one layer of mailtrays at a time to gently slide from the chute 129 onto the conveyor,without damaging the mail trays and other types of packages.

[0036] Method of Unloading Mail Trays from the Unloading System of thePresent Invention

[0037] FIGS. 4 though 7 show the various stages of operation of thepresent invention. In FIG. 4, the holding structure 100 is opened, via ahinge 140, in order to accommodate the cart 106 on the bottom supportingsurface 104. In FIG. 5, the holding structure 100 is closed such thatthe cart 106 is now enclosed therein. In FIG. 6, the system of thepresent invention is lifted and then tilted toward the conveyor. In thisfigure, it is shown that the reverse hinge portion 112, upon contactingthe floor, continues to move away the bottom supporting surface 104.This ensures that the gate 108 will not be hindered during the openingoperation. In FIG. 7, the gate 108 begins to slide downward to thus formthe chute 129. The chute 129, in combination with the ramp 110 and tiltangle, ensures that the mail trays or other mail packages will gentlyslide from the cart 106 and onto the conveyor. Additionally, during thisoperational stage, the controller controls the tilting mechanism 124,lifting mechanism 126 and the gate 108. Also, the limit switches 138 andthe photoeyes 131, controlled by the controller 136, ensure that themail trays and other mail packages are metered, in a controlled manner,from the unloading system 100 to the conveyor.

[0038] The cycle time for unloading the mail trays onto the conveyor maybe set to a maximum of approximately 90 seconds, although other cycletimes are also contemplated by the present invention. The holdingstructure is also designed to accommodate mail trays of varying sizesand shapes, and it should thus be understood that the present inventionshould not be limited to any particular size.

[0039]FIG. 8 is a flow diagram showing the steps of implementing themethod of the present invention. The steps may be implemented oncomputer program code in combination with the appropriate hardware. Thiscomputer program code may be stored on storage media such as a diskette,hard disk, CD-ROM, DVD-ROM or tape, as well as a memory storage deviceor collection of memory storage devices such as read-only memory (ROM)or random access memory (RAM). FIG. 8 may equally represent a high levelblock diagram or a control system of the present invention, implementingthe steps thereof.

[0040] In particular, in step 802, the operator loads the system of thepresent invention. In one embodiment, this may include opening the door,placing the mail cart on the bottom supporting surface and thereafterclosing and locking the door. In another embodiment, this may includeopening the entire holding structure, as shown in FIG. 4, and placingthe mail cart on the bottom supporting surface and thereafter closingand locking the holding structure. In step 804, the system begins totilt to approximately 30° from the horizontal. In step 806, the limitswitch is used to determine when there is a proper tilt angle. If thereis not a proper tilt angle, then steps 804 and 806 repeat. If there is aproper tilt angle, in step 808, the gate is incrementally moved orretracted downward in order to allow one layer of mail trays to gentlyexit the chute and onto the conveyor.

[0041] In step 810, the photoeyes determine whether the entire layer ofmail trays is on the conveyor. If the photoeyes are blocked (mail trayson the conveyor adjacent to the unloading area), then the gate isstopped and until the photoeye is unblocked (step 812). This allows themail trays to be conveyed away from the unloading system of the presentinvention thereby preventing a pile up of mail trays. When the photoeyesare not blocked, then, in step 810, the gate continues to open allowinganother layer of items to slide down onto the conveyor. In this manner,the unloading of the items is metered so that the cart contents are notunloaded into a pile (i.e., piggy backed) on the conveyor. Now, in step814, a determination is made as to whether the gate has been fullyopened. This is accomplished when the photoeye becomes tripped by theramp at the front of the gate. If the gate is not fully retracted, thenthe control of the present invention may revert back to step 808. Thensteps 808 through 812 repeat until the gate is fully retracted. If thegate is filly retracted, then the gate will stop and be raised to itsclosed, original position (step 816). In step 818, the holding structureof the present invention will then tilt back to its original position.

[0042] While the invention has been described in terms of preferredembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theappended claims.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent is as follows:
 1. A method of unloading productfrom an intermediate container mechanism onto a conveyor for downstreamprocessing, the unloading mechanism including a holding structure havinga gate slidable between an open position and a closed position, themethod including the steps of: (a) loading a mail cart having productinto the holding structure; (b) tilting the holding structure to arelative angle with respect to a supporting surface; (c) incrementallyopening the gate to allow a single layer of product to slide from themail cart and exit from the holding structure onto the conveyor; (d)determining whether the single layer of product has exited from theholding structure and onto the conveyor; (e) if the step (d) isaffirmative, repeating the steps of (c) and (d) until the gate hasreached it full open position.
 2. The method of claim 1, furthercomprising the step of determining whether the relative angle of theholding structure is at approximately 30° with respect to the supportingsurface.
 3. The method of claim 1, further comprising the step ofraising the gate to the closed position and returning the holdingstructure to an original position after the gate has been fully openedas determined by a sensor.
 4. A control system for controlling theunloading of product from an unloading mechanism onto a conveyor fordownstream processing, the control system comprising: (a) a module thatcontrols tilting of the unloading mechanism to a relative angle withrespect to a supporting surface; (b) a module that incrementally opens agate of the unloading mechanism to allow a single layer of product toslide from a mail cart within the unloading mechanism and exit therefromonto the conveyor; and (c) a module that controls determining whetherthe single layer of product has exited from the unloading mechanism andonto the conveyor and if the step (c) is affirmative, repeating thesteps of (b) and (c) until the gate has reached it full open position.5. The control of claim 4, wherein the module that controls tiltingfurther controls determining whether the relative angle of the unloadingmechanism is at approximately 30° with respect to the supportingsurface.
 6. The control of claim 4, wherein the control that controlsincrementally opening of the gate further controls raising the gate tothe closed position.
 7. The control of claim 4, further comprising amodule that controls a relative angle of the unloading mechanism is atapproximately 30° with respect to the supporting surface.
 8. The controlof claim 4, further comprising a module that controls raising the gateto the closed position and returning the unloading mechanism to anoriginal position after the gate has been fully opened as determined bya sensor.
 9. A machine readable medium containing code for performingunloading of product from an unloading mechanism onto a conveyor fordownstream processing, the code implementing the steps of: (a) tiltingthe unloading mechanism to a relative angle with respect to a supportingsurface; (b) incrementally opening a gate of the unloading mechanism toallow a single layer of product to slide from a mail cart within theunloading mechanism and exit from therefrom onto the conveyor; and (c)determining whether the single layer of product has exited from theunloading mechanism and onto the conveyor and if the step (c) isaffirmative, repeating the steps of (b) and (c) until the gate hasreached it full open position.